class code4 {
    int ret = Integer.MAX_VALUE;
    public int minDepth(TreeNode root) {
        if(root == null) {
            return 0;
        } else if(root.left == null) {
            return minDepth(root.right)+1;
        } else if(root.right == null) {
            return minDepth(root.left)+1;
        } else {
            return Math.min(minDepth(root.left), minDepth(root.right)) + 1;
        }
    }
}